1. Field of the Invention
This invention relates to the general field of basic catalysis of organic reactions and is particularly concerned with catalysts for promotion of reactions involving organic isocyanates, as in the production of polyisocyanurates and polyurethanes.
2. Prior Art
The reaction of organic isocyanates with hydroxyl compounds is well known to be accelerated by tertiary amines and other suggested catalysts. These reactions are employed extensively in the production of polyurethane foams wherein the foaming action is initiated by an external blowing agent incorporated in the formulation or by reaction of the isocyanate with included water to release carbon dioxide.
While studies have been carried out to determine the relative basicity and other properties of tertiary amines proposed for use as catalysts in reactions involving organic isocyanates, the data so obtained has proven to be of little value in predicting their degree of suitability or effectiveness in commercial formulations for the production of desired polyurethanes or polyisocyanurates.
The use of quaternary ammonium compounds in the production of polyurethane resins is also disclosed in the art; for example in U.S. Pat. Nos. 2,779,689 and 2,981,700; wherein the activity depends upon their decomposition to liberate the corresponding tertiary amines. Typical of these suggested quaternary ammonium compounds are the salts formed by reaction of a tertiary amine, such as N-methyl morpholine, with acid anhydride. The obtained quaternary salts of this type, in general, have lower catalytic activity than the tertiary amines from which they are derived.
Fabris et al in U.S. Pat. No. 3,726,816 lists a number of quaternary ammonium bases stated to be known in the art as catalysts in polyurethane reactions, including among these benzyl trimethyl ammonium hydroxide and heterocyclic quaternary ammonium hydroxides such as N-methyl pyridinium hydroxide and morpholinium bases. The patent also mentions the corresponding alkoxides, aryloxides and aralkoxides as exemplified, among others named, by benzyltrimethyl ammonium methoxide and ethoxide, and tetramethylammonium phenoxide. The patent proposes the use of these quaternary ammonium bases in polyurethane formulations in conjunction with compounds effective in neutralizing the quaternary base, as to produce low odor polyurethane foams.
Erner, in U.S. Pat. No. 3,010,963, discloses the preparation of quaternary hydroxyalkyl bases of diazabicyclo-octane and of imidazole by reacting the corresponding diazine or diazole with alkylene oxide and water. The obtained quaternary hydroxide can be further reacted with mineral or organic acid to produce salts. Thus, the patent describes the production of N,N'-bis hydroxy propyl diazabicyclo-octane dihydroxide and conversion of the same to salts by reaction respectively with sulfuric, cresylic, salicylic and phosphoric acids. The sulfates and phosphates are stated to have powerful inhibitory action on the growth of certain microorganisms such as yeasts, molds and sactobacilli. The patent does not describe any specific use for the organic acid salts. In another example of the patent, the quaternary hydroxide obtained by reaction of 2-methyl imidazole with propylene oxide and water, is converted to the acetate salt, which was tested as a polymerization promoter in polyurethane foam reactions when used in association with the theretofore known diazabicyclo-octane catalyst.
Lambert et al, U.S. Pat. No. 3,108,975, is concerned with the production of water blown polyurethane foams from polyether polyols having predominantly secondary hydroxyl end groups. The patent proposes for use as catalysts in this reaction, optionally in the presence of known tertiary amine catalysts, certain basic compounds such as hydroxides of alkali or alkaline earth metals, or of fully substituted quaternary ammonium radicals; or salts of the foregoing. Among the quaternary ammonium radicals listed are those of N-methylpyridinium, benzyltrimethyl ammonium and trimethyl cyclohexyl ammonium. Among possible salts, the patent lists generally alkoxides, phenoxides, carboxylates, carbonates and others. The patent contains no specific example using quaternary ammonium phenoxide or alkoxide in the production of polyurethane or in other polyisocyanate reactions.
In a companion application of Bechara, Ser. No. 377,446, filed July 9, 1973, now abandoned there are disclosed methods for synthesis of certain acyclic quaternary hydroxyalkyl ammonium alkoxides and phenoxides useful, among other suggested purposes, as catalysts for making polyurethane and polyurethane-polyisocyanurate foams. The therein disclosed compounds correspond to the general formula: ##EQU3## wherein: R.sub.5 is selected from the group consisting of H, alkyl of 1 to 2 carbon atoms and aryl or aralkyl group of 6 to 10 carbon atoms, and in which
R, r.sub.1 and R.sub.2 may be independently alkyl, hydroxyalkyl, aryl, aralkyl or cycloalkyl, and R.sub.3 and R.sub.4 are independently H, alkyl, aryl or aralkyl. PA1 R.sup.1 is H or an alkyl group of 1 to 10 carbon atoms, PA1 R.sup.2 is H or an alkyl or aryl group of 1 to 10 carbon atoms, and PA1 .phi. is a phenyl group which may be further substituted by one or more hydroxyl or alkyl groups.
The use of the foregoing compounds of formula (I) as catalysts, is claimed in the continuation-in-part of the present application, Ser. No. 377,447 now U.S. Pat. No. 3,892,687.